How to Grow Verbascum
Verbascum bombyciferum
Verbascum bombyciferum is a dramatic architectural plant that forms a large silvery-felted rosette in its first year, then sends up towering flower spires to 2m in the second. It thrives in full sun and poor, well-drained soil — perfect for gravel gardens and dry borders where it self-seeds to maintain a permanent colony. Do not feed or overwater — lean conditions produce the best silver foliage and sturdiest spires. Allow some seed heads to remain for self-sowing, or deadhead to prevent excessive spread.
Yearly Lifecycle
Care Essentials
Rarely needed — thrives in poor, dry soil. Avoid rich feeding which produces soft growth prone to flopping and reduces the silvery felted appearance of the leaves.
Watch For
- Mullein moth caterpillars (distinctive spotted larvae)
- Powdery mildew in humid conditions
- Self-seeding can be prolific
Companions
Eryngium, Stachys byzantina, Lavender, Ornamental Grasses
Care Requirements
Light
Full sun, hot and dry
Needs at least 6 hours of direct sun. Thrives in the hottest, driest spots in the garden including south-facing walls and gravel.
Watering
Very low, drought-tolerant
Water only to establish. Once settled, rainfall is sufficient. Overwatering causes root rot and floppy growth.
Fertilizing
None needed
Thrives in poor soil. Feeding produces soft, leggy growth that flops and reduces the silvery leaf texture.
Pruning
Cut main spike after flowering
Remove the spent main flower spike to encourage side shoots. Cut the whole plant to ground level in late autumn once it dies back.
Growing Tips
Biennial lifecycle — plan for succession
Each plant flowers once then dies. Allow self-seeding or sow fresh seed annually to maintain a continuous display. You will always have rosettes and flowering plants together.
Poor soil produces the best plants
Rich soil and feeding make verbascum tall, floppy, and less silvery. The best specimens grow in gravel, rubble, or thin chalky soil with no supplemental feeding.
Watch for mullein moth caterpillars
The distinctive spotted yellow-and-black caterpillars can strip leaves quickly. Pick off by hand if numbers are small, or tolerate the damage — the plant usually survives.
Cut main spike to extend flowering
After the main flower spike finishes, cut it back to encourage smaller side spikes that extend the display by several weeks.
Popular Varieties
Southern Charm, Sugar Plum, Clementine, Gainsborough, Dark Eyes, Helen Johnson
